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APPENDIX                                     293

2.     i>y  distillation with  potassium cyanide, the nitriles are

(V.N-.SO.jK  |   KCN = (yir.CN -I- K,,SOa.
ii   >     <                         i)   i)               j     j

3.   11 y   fusion with sodium   formate, the   sulphonic  group is
replaced by carboxyl,

r,;Il:iS():,Na   !   IICOONa ---C,lI5COONaH- NallSOg.

4   l>y the action of phosphorus pentachloride the sulphonic
chloride is obtained,

rt;U,S()3K -I   VL\ = (yiflSOXl + POC13 + KC1.


Benzenesnlphonic Chloride. The sulphonic chlorides
differ from the carboxylic chlorides in being" very slowly decom-
posed by water. They read, however, in an analogous fashion
with alcohols, phenols, and amines in presence of caustic soda.

The behaviour of primary, secondary, and tertiary amines
has been sut^ested as a basis of separation of these three classes
of compounds. The primary amines usually form compounds
with tin1 sulphonic chloride, which dissolve in caustic soda ; the
derivatives of the secondary amine are insoluble, whereas the
tertiary amines do not re;ict with the sulphonic chloride (Hins-
bcr^). The* method cannot always be employed.

On reduction of the sulphonic chloride with zinc dust and
water, the xinc salt of the sulphinic acid is formed,

2('(jIIfiS(),,ri -I- 2/n = (Q.II-iSO.J.jXn + XnCl2.

The arid is separatee! from the xinc salt by boiling with
sodium carbonate, filtering from xinc carbonate, and decom-
posing the soluble sodium salt with sulphuric acid, which pre-
cipitates the sulphinic acid.

The sulphinic acids are unstable compounds. They are readily
oxidised to sulphonic acids ; on fusion with alkalis they are con-
verted into the hydrocarbon and alkaline sulphite,

CI!.S().N:i + NaOII =

on reduction they form thiophenols,
*             Ct;ll,rS(UI -i  2llo -- QIUSIl -I   2lloO.